Thanks Andrew!
I know what is the delegation and how to use it. Im using this authentication method with iis7 ftp, but on the same site I cant authenticate through webdav the same users.
I added the users to the site's WebDAV Authoring Roles, and to the IIS Manager Permissons (it needed for the ftp too). WebDAV is enabled for the site. Authorization Rules: All Users. Authentication: Basic, Windows, Anonymous enabled. (WebDAV works with windows users!!) Should I add any other settings to work with IIS Manager Users?